Measurements of physical and chemical attributes of water bodies are commonly made by lowering instruments from a surface vessel to the bottom of a body of water such as the ocean, a lake, or a river. Water depths can range from a few meters to nearly ten thousand meters. The location from which the data is taken is commonly referred to as a hydrographic station. The water properties can change substantially over time. Therefore, the frequency of measurement needs to be commensurate with the rate of change of the water properties.
The frequency by which these measurements can be made is governed by the logistics of re-occupying the observation locations or stations. It is now recognized that a number of important ocean circulation and limnological phenomena occur episodically, and that there are short and long-term changes in water properties. More frequent sampling, or sampling initiated by a measured change in the environment, is needed to elucidate ocean or lake behavior.
While such frequent measurements have been extremely difficult to obtain, the limited number of studies that have re-occupied the same site many times over a period have proven to be extremely valuable. For example, an investigation by J. R. Lazier in 1980 of the Labrador Sea documented the effect of low-salinity surface water on deep water convection. Undoubtedly, many other important discoveries concerning ocean water circulation await the ability to obtain long-term profiles of water properties. There remain to date scientific and operational needs for sustained ocean observations at fixed locations. Despite advances in drifting, gliding, and self-propelled autonomous instruments, use of these technologies to form “virtual moorings” over long time periods are only practical in modest ocean current environments. Long-term measurements at fixed locations are traditionally made using moored instrument systems. At a limited number of preselected depths, an instrument package is affixed to the mooring cable which is anchored to the sea floor. Traditional moored profilers are deployed on a bottom-anchored mooring; therefore, they generally remain on station even in strong flows, but their functionality is limited. For example, while the traditional profiler may be preferable to single observations, the profile over time is severely constrained by a limited number of sampling depths. Maintaining calibration of many instrument packages is time-consuming and expensive. Since each preselected depth requires its own complete instrument package, the cost to obtain the data increases proportionately to the number of sites selected.
It has been recognized that a single sensor platform that can move up and down the mooring cable may provide distinct advantages by eliminating the need for multiple sensors and multiple tethering systems. It may also provide the advantages of a single calibration applicable to all of the measurements. This is particularly important in long-term measurements where sensor drift over time may be large compared to the ocean variability.
Previous moored profiler models have been in use for the past two decades to address the need or desire to observe water properties and currents at fixed geographic locations. These profilers are traditionally propelled vertically on a mooring cable using a traction drive wheel. While these models have returned unique and valuable observations, such models have also suffered from endurance issues (often less than 1,000 km of profiling per deployment). This endurance problem is particularly problematic as profilers are routinely meant to be disposed in the water column for time periods of a year or longer. Additionally, these profilers lack the ability to provide reliable track records for profiling. It would be desirable for a profiler to fully span its programmed sampling depth range especially during times of strong incident ocean currents. Likewise, traditional profilers have suffered great issues with reliability with regards to data collection and retention. A frustrating number of mooring profiler deployments have returned incomplete profiles and/or sampled for less than planned periods due to issues such as premature battery depletion. Given the number of variables at play in an ocean environment, a failed or only partially successful deployment means, from a scientific standpoint, the complete loss of information that will likely never be acquired or duplicated. These performance issues have dampened community interest in using and inventing in profilers.
Existing moored systems also suffer from a number of other functional defects. For example, they routinely fail to reach bottom stop depth while having limits on depth of operation. Others slip by losing traction of the drive wheel. Still others have suffered from lost performance in strong water currents. As a whole, the units have been unreliable at times, either concerning the ability to stay at specific depth when resting between profiles or inconsistent profiling speeds or unreliable time series and data collection which causes profiles to exceed allotted amounts of batter power.
Therefore, there is an unmet need for a re-designed mooring profiler able to better support oceanographic research and industrial programs that, in one or more embodiments, is adapted for use in strong current conditions with increased reliability and length of deployment in addition to a higher quality data return. A redesigned Articulating Moored Profiler System is provided herein which, in one or more embodiments, seeks to provide at least one of the following benefits: (1) improved profiling reliability across various environments, including stronger flows and in instances of misballasting; (2) increased profiler endurance; (3) a more flexible layout in relation to where sensors can be mounted onto or inserted into the profiling vehicle which may include the ability to place sensors outside the fluid boundary layer of the vehicle; (4) a streamline sensor interface which can improve the operator interface and/or enhance the flexibility of data logging; and (5) a more robust and better quality brake system.